MIC-A polymorphism and a MIC-A-MIC-B null haplotype with ~ 100-kb deletion

The MHC class I chain-related gene (MIC) family has been identified as a new gene family in the HLA-B region. MIC-A shows a high degree of polymorphism, and more than 30 alleles have been reported. In the present study, we analyzed the polymorphisms of exons 2, 3, and 4, which encode αl, α2, and α3 domains, using PCR-single-strand conformation polymorphism methods and nucleotide sequencing in the Japanese population. Eight MIC-A alleles were observed, in which one allele, tentatively named MIC-AMW, was new. A strong linkage disequilibrium was observed between the MIC-A and HLA-B loci, with the exception that B*3901 showed association with multiple MIC-A alleles. Interestingly, a MIC-A-MIC-B null haplotype, which is strongly associated with B*4801, was also identified. In this haplotype, a large-scale deletion (of approximately 100 kb) including the entire MIC-A gene was indicated and the MIC-B gene (MIC-B0107N) possessed a stop codon.